Wafer processing hardware for epitaxial deposition with reduced auto-doping and backside defects

ABSTRACT

According to one aspect of the invention, an apparatus for reducing auto-doping of the front side of a substrate and reducing defects on the backside of the substrate during an epitaxial deposition process for forming an epitaxial layer on the front side of the substrate comprising: a means for forming a wafer gap region between the backside of the substrate and a susceptor plate, having an adjustable thickness; a means for ventilating auto-dopants out of the wafer gap region with a flow of inert gas, while inhibiting or prohibiting the flow of inert gas over the front side of the substrate; and a means for flowing reactant gases over the surface of the front side of the substrate, while inhibiting or prohibiting the flow of reactant gases near the surface of the backside of the substrate.

BACKGROUND OF THE INVENTION

1). Field of the Invention

Embodiments of the invention relate to the apparatus and method of usingthe apparatus for processing semiconductor substrates. In particular,the apparatus and method of using the apparatus for the deposition of anepitaxial semiconductor layer with reduced auto-doping and backsidedefects.

2). Background

FIG. 1A relates to an epitaxial processing apparatus 100 that may beused for epitaxial deposition. Substrate 102, which may be heated byupper heat lamps 106, is positioned over a susceptor 104, which may beheated by lower heat lamps 107. Upper dome 108 and lower dome 109, whichmay be quartz, enclose the processing chamber 113. Lift arms 101 andsusceptor arms 105 move so as to separate from each other, thusseparating the substrate 102 from the susceptor 104, and so as toposition the processed substrate 102 to be removed from the processingchamber 113 by a robot (not shown) and replaced by an unprocessedsubstrate 102.

The epitaxial deposition of a low doped semiconductor layer on a highlydoped substrate may often result in substantial auto-doping of theepitaxial low doped layer. Referring to FIG. 1B, during a hightemperature epitaxial deposition process, dopant from the backside ofthe substrate 102 may diffuse out of the substrate 102 and into thewafer-susceptor gap 112. With a build-up of dopant in thewafer-susceptor gap 112, some dopant may migrate around the edge of thesubstrate 102 to the topside of the substrate 102, where the epitaxiallayer is being formed. This phenomena is known as auto-doping 110 andresults in the auto-dopants 110 mixing into the epitaxial layer beingformed, particularly near the edge of the substrate 102. FIG. 1Cdemonstrates the auto-doping effect on resistivity 111. The extraauto-dopants 110 result in lowering the resistivity of the epitaxiallayer near the edge, thus limiting the maximum resistivity of theepitaxial layer that may be formed on a highly doped substrate 102. Thisproblem is particularly acute when boron is the dopant in a highly dopedP+ substrate 102.

Oxidizing the backside of the substrate 102 may help seal the backsideof the P+ substrate 102, thus reducing the out-diffusion of dopant intothe wafer-susceptor gap 112. Backsealing may be effective, however thisapproach may be expensive because the oxide must be deposited and thenremoved, thus requiring at least two extra steps.

Another approach involves lowering the processing temperature during theepitaxial deposition process, thus substantially lowering theout-diffusion of dopant into the wafer-susceptor gap 112. Although thisapproach may be effective in reducing auto-doping, it also substantiallyreduces the rate of epitaxial growth on the substrate 102, thussubstantially reducing throughput.

One approach involves adding more dopant to the middle of the wafer toprovide a more uniform resistivity across the entire wafer. However,this process is only effective for the deposition of a low resistivityepitaxial layer. The process is limited to an epitaxial layer in therange of only about 1.5 to 3.0 ohms/sq.

SUMMARY

The present invention is related to an apparatus for reducingauto-doping of the front side of a substrate and defects on the backsideof the substrate during an epitaxial deposition process for forming anepitaxial layer on the front side of the substrate. In embodiments, thesubstrate may be heavily doped. In embodiments, the substrate maycomprise heavily doped single crystal silicon or single crystalsilicon-germanium material. In embodiments, the epitaxial layer maycomprise lightly doped single crystal silicon or single crystalsilicon-germanium material. Embodiments may comprise: a means forforming a wafer gap region having an adjustable thickness, wherein thewafer gap region may comprise a region between the backside of thesubstrate and a susceptor plate; a means for ventilating auto-dopantsout of the wafer gap region with a flow of inert gas, while inhibitingor prohibiting the flow of inert gas over the front side of thesubstrate; and a means for flowing reactant gases over the surface ofthe front side of the substrate, while inhibiting or prohibiting theflow of reactant gases near the surface of the backside of thesubstrate.

Some embodiments, relate to providing a wafer gap region between thebackside of the substrate and the susceptor plate. In embodiments, thewafer gap region may be ventilated, so as to remove auto-dopants. Someembodiments provide a barrier between the flow of inert gas and the flowof reactant gases. Embodiments relate to reducing the concentration ofauto-dopants incorporated into the lightly doped epitaxial semiconductorlayer on the front side of the substrate, where the epitaxial layer isbeing deposited.

Embodiments may provide the means for ventilating the wafer gap regionthat may comprise flowing substantial amounts of inert gas through thewafer gap region. Flowing substantial amounts of inert gas through thewafer gap region may provide that mixing of inert gas with auto-dopantsis the predominant mechanism by which auto-dopants may be removed fromthe wafer gap region.

Embodiments may provide a method of using an epitaxial apparatus thatsupports a substrate above a susceptor plate for depositing an epitaxiallayer on the substrate, which may comprise providing a spacer and awafer processing structure onto a susceptor in a processing chamber ofan epitaxial reactor apparatus; wherein the wafer processing structuremay comprise a wafer support ring and a wafer holder structure attachedto the wafer support ring; providing a substrate; wherein the substratecomprises a front side and a backside; wherein the spacer may be incontact with the wafer support ring and positioned on the susceptorplate, wherein the spacer may position the wafer support ring above thesusceptor plate to provide a wafer gap region between the susceptorplate and the backside of the substrate; wherein the backside of thesubstrate may comprises a heavily doped semiconductor; flowing an inertgas into the processing chamber proximate to the wafer gap region andbelow the backside of the substrate; flowing reactant gases into theprocessing chamber onto the front side of the substrate; growing alightly doped epitaxial semiconductor layer on the front side of thesubstrate from the reactant gases; and exhausting the inert gascontaining auto-dopants out from the wafer gap region and below the topof the wafer processing structure out of the processing chamber.

Embodiments may further comprise adjusting the wafer gap region, bymeans of adjustable spacers. Embodiments may comprise reducing theconcentration of auto-dopants in the wafer gap region and providingbarriers to keep the flows of reactant gases separate from the flow ofinert gas, thus reducing the risk of incorporating auto-dopantcontaminants into the lightly doped epitaxial semiconductor layer on thefront side of the substrate and reducing the deposition of epitaxialmaterial on the backside of the substrate. Embodiments may furthercomprise rotating the susceptor plate, the wafer processing structure,and the substrate during the deposition of the epitaxial layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1A illustrates a cross-sectional view of a prior art epitaxialprocessing chamber and apparatus.

FIG. 1B illustrates a cross-sectional view of a prior art susceptor witha wafer.

FIG. 1C illustrates a resistivity profile of a prior art deposition ofan epitaxial layer exhibiting auto-doping.

FIG. 2A illustrates a three dimensional view of embodiments comprising awafer processing structure installed on a susceptor plate.

FIG. 2B illustrates an exploded three-dimensional view of embodimentscomprising a wafer processing structure on a susceptor plate.

FIG. 2C illustrates a cross-sectional view of embodiments comprising awafer processing structure holding a wafer on a susceptor plate.

FIG. 3A illustrates an exploded 3-D view of embodiments comprising awafer processing structure with a skirt on a susceptor plate.

FIG. 3B illustrates a cross-sectional view of embodiments comprising awafer processing structure with a skirt holding a wafer on a susceptorplate.

FIG. 4 illustrates a cross-sectional view of embodiments comprising anadjustable standoff pin positioned in a susceptor plate.

FIG. 5A illustrates a 3-D view of embodiments comprising a waferprocessing structure with a skirt having vents on a susceptor plate alsohaving vents.

FIG. 5B illustrates a cross-sectional view of embodiments comprising awafer processing structure with a skirt having vents holding a wafer ona susceptor plate also with vents.

FIG. 6 illustrates an enlarged cross-sectional view of embodimentscomprising part of a wafer processing structure with a skirt and aspacer holding a wafer on a susceptor plate.

FIG. 7 illustrates a cross-sectional view of embodiments comprising awafer processing structure with a shelf extension and a skirt havingvents holding a wafer on a susceptor plate with vents.

FIG. 8 illustrates a cross-sectional view of embodiments comprising awafer processing structure with a skirt holding a wafer on a susceptorplate with lift fingers used to load and unload wafers.

FIGS. 9A to 9E illustrate cross-sectional views of various embodimentsof a wafer holder structure.

FIG. 9F illustrates a top view of embodiments of a wafer holderstructure.

FIGS. 10A and 10B illustrate cross-sectional and top views ofembodiments of spacer rings having vents.

FIG. 10C illustrates a cross-sectional view of embodiments of a skirthaving an asymmetrical distribution of vents.

FIG. 10D illustrates a cross-sectional view of embodiments of a skirthaving an asymmetrical length.

FIG. 10E illustrates a top view of embodiments of a skirt having turbineblades and vents.

FIG. 11 illustrates a cross-sectional view of embodiments of a waferprocessing structure within an epitaxial deposition apparatus.

FIG. 12 illustrates a flow chart of embodiments of a method of using theepitaxial deposition apparatus.

FIG. 13 illustrates an epitaxial processing apparatus with an embodimentof a wafer holder.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionwill be described, and various details set forth in order to provide athorough understanding of the present invention. However, it would beapparent to those skilled in the art that the present invention may bepracticed with only some or all of the aspects of the present invention,and the present invention may be practiced without the specific details.In other instances, well-known features are admitted or simplified inorder not to obscure the present invention.

It should be understood that FIGS. 1A through 13 are merely illustrativeand may not be drawn to scale. While certain exemplary embodiments havebeen described and shown in the accompanying drawings, it is to beunderstood that such embodiments are merely illustrative and notrestrictive of the current invention, and that this invention is notrestricted to the specific constructions and arrangements shown anddescribed since modifications may occur to those ordinarily skilled inthe art.

Reference in this specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The appearances of the phrase “in one embodiment” invarious places in the specification are not necessarily all referring tothe same embodiment, nor are separate or alternative embodimentsmutually exclusive of other embodiments. Moreover, various features aredescribed which may be exhibited by some embodiments and not by others.Similarly, various requirements are described which may be requirementsfor some embodiments but not other embodiments.

Some embodiments anticipate the application of the invention in any hightemperature process where contaminants from the backside of a substratecontaminate the front side of the substrate, such as in chemical vapordeposition (CVD) processes and in the formation of silicon-on-insulator(SOI) substrates. However, most embodiments discussed will generallyrelate to epitaxial deposition apparatus and processes, but are notintended to limit the embodiments to only epitaxial apparatus andprocesses. In embodiments, the substrate may comprise a heavily dopedmaterial. In embodiments, the heavily doped substrate may comprise aheavily doped semiconductor. In embodiments, the substrate may comprisea heavily doped single crystal silicon or single crystalsilicon-germanium material. In embodiments, the substrate may comprise asilicon on insulator substrate. In embodiments, the epitaxial layer maycomprise lightly doped single crystal silicon or single crystalsilicon-germanium material.

Embodiments, illustrated in FIG. 2C, relate to providing a wafer gapregion 215 between the backside of the substrate 202 and the susceptorplate 205, which may be used in a reduced auto-doping epitaxialapparatus 1300, illustrated in FIG. 13. In embodiments, the wafer gapregion 215 may be ventilated, so as to remove auto-dopants 217. Further,some embodiments provide a barrier between the flow of inert gas 218,219 and the flow of reactant gases 221, 222. In embodiments, thereactant gases 221 may comprise a silicon precursor gas used to form asingle crystal silicon or single crystal silicon-germanium epitaxiallayer. Embodiments of a silicon precursor gas may comprise SiH₄ orsilane gas. In embodiments, the reactant gases 221 may further comprisea germanium precursor used to form a single crystal silicon-germaniumepitaxial layer. Embodiments of a germanium precursor gas may compriseGeH₄. In embodiments, the reactant gases 221 may further comprise one ormore dopant precursors used to dope the single crystal epitaxial layer.Embodiments of a dopant precursor gas may comprise diborane or borane.Reactant gases 221 for forming and doping an epitaxial layer may be wellknown in the art.

Ventilating the wafer gap region 215 may result in a substantialreduction of the concentration of auto-dopants 217 in the wafer gapregion 215. A reduction in the concentration of auto-dopants 217 mayreduce the amount of auto-dopants 217 that may migrate to the front sideof the substrate 202 and contaminate the epitaxial layer being formed onthe substrate 202. In some embodiments, a barrier between the backsideand front side of a substrate 202, may also reduce the amount ofauto-dopants 217 that may migrate to the front side of the substrate 202and contaminate the epitaxial layer.

A barrier between the backside and front side of a substrate 202, mayhelp isolate the flow of reactants 221, 222 to the front side of thesubstrate 202 and away from the backside. Isolating reactants 221, 222from the backside of the substrate 202 may reduce the deposition ofepitaxial material onto the backside of the substrate 202. Epitaxialmaterial deposited on the backside of a substrate 202 may likely need tobe removed in subsequent processes so that the substrate 202 can lieflat, which is particularly important in lithographic processes wherethe imaging plane is important. In addition to the extra costsassociated with extra processing steps, such as etching the backside ofthe substrate 202, there is also an increase in the risk of formingbackside defects, such as scratches and haze.

FIG. 2A illustrates a 3-D view of embodiments of a wafer processingstructure 200 installed on a susceptor plate 205, which may be used in areduced auto-doping epitaxial apparatus 1300, illustrated in FIG. 13.The wafer processing structure 200 supports a substrate 202 above asusceptor plate 205. The wafer processing structure 200 comprises awafer support ring 220 and a wafer holder structure 203 attached to thewafer support ring 220, wherein the wafer holder structure 203 supportsthe substrate 202 in a position for processing. In some embodiments, thewafer support ring 220 may be positioned by adjustable stand-off pinspacers 212, which are inserted into stand-off pin slots 213 located inthe susceptor plate 205. In some embodiments, the positioned wafersupport ring 220 may be approximately parallel to the susceptor plate205. In some embodiments, the wafer processing structure 200 is slightlyinclined with respect to the susceptor plate 205, wherein the substrate202 held by the wafer processing structure 200 is slightly lower on theinjection side and slightly higher on the exhaust side. In theembodiments illustrated in FIG. 2C, the wafer holder structure 203 maybe a shelf and may be constructed with the wafer support ring 220 as asingle unit.

Embodiments of the wafer support ring 220 may comprise one or morematerials selected from a group consisting of: silicon carbide, quartz,graphite, silicon nitride, aluminum nitride, or any combination thereof.Embodiments of the wafer holder structure 203 may comprise one or morematerials selected from a group consisting of: silicon carbide, quartz,graphite, silicon nitride, aluminum nitride, or any combination thereof.Embodiments of the spacer 212 may comprise one or more materialsselected from a group consisting of: silicon carbide, quartz, graphite,silicon nitride, aluminum nitride, or any combination thereof. In someembodiments, any components, or any combination of components, of thewafer processing structure 200 may comprise one or more materialsselected from a group consisting of: silicon carbide, quartz, graphite,silicon nitride, aluminum nitride, or any combination thereof.

In some embodiments, any components, or any combination of components,of the wafer processing structure 200 may be constructed of materialsthat are thick enough to maintain structural integrity for handling andto endure the epitaxial process, but thin enough to provide a lowthermal mass for the wafer processing structure 200. A low thermal massof the wafer processing structure 200 may provide a quick heat up andcool down of the wafer processing structure 200. Rapid heating andcooling of the wafer processing structure 200 may help to facilitate thequick heat up and cool down of the substrates 202 being processed.Throughput of the epitaxial apparatus may increase with a low thermalmass wafer processing structure 200. In embodiments, the thickness ofthe walls of the wafer support ring 220 may be between about 0.002inches to about 0.3 inches. In an embodiment, the thickness of the wallsof the wafer support ring 220 may be about 0.005 inches to about 0.015inches.

Embodiments in FIG. 2C, illustrate that the topside of the susceptorplate 205, which faces the backside of the substrate 202, may beapproximately flat. A susceptor plate 205 with a flat topside may resultin improved temperature uniformity across the substrate 202. The growthrate of an epitaxial layer depends on the temperature of the substrateduring processing. Therefore, improved temperature uniformity may likelyresult in improved thickness uniformity across the substrate 202.

FIG. 2B illustrates an exploded view of embodiments wherein the wafersupport ring 220 and the spacer 212 are detachable from the susceptorplate 205. Some embodiments provide spacers 212, which are adjustable,thereby adjusting the thickness of the wafer gap region 215. Inembodiments illustrated in FIGS. 2B and 2C, the spacer comprises astand-off pin 212. In an embodiment illustrated in FIG. 4, the stand-offpin 212 comprises a pin protrusion 417, which fits into a stand-off pinslot 213 in the susceptor plate 205. In an embodiment, pin lips 418 reston the susceptor plate 205, which may provide a means to precisely andconsistently fix the spacer height above the susceptor plate 205. In anembodiment, pin screws 216 may be used to attach the stand-off pinspacers 212 to the wafer support ring 220. FIG. 3B illustrates anembodiment wherein the stand-off pin spacers 212 are attached by pinscrews 216 to a support ring skirt 301. In an embodiment, the stand-offpin spacers 212 are detachable from the wafer support ring 220 and canbe replaced with different sized stand-off pin spacers 212. Therefore,the thickness of the wafer gap region 215 may be adjusted by usingdifferent spacers 212. In embodiments, the wafer gap region 215 has athickness of about 0.1 inches to about 0.3 inches. In an embodiment, thewafer gap region 215 has a thickness of about 0.15 inches to about 0.25inches.

FIG. 2C illustrates embodiments wherein auto-dopants 217 may diffuse outfrom the backside of substrate 202 and into the wafer gap region 215.The wafer gap region 215 may be ventilated by injected inert gas 218,wherein the auto-dopants 217 mix with the injected inert gas 218, whichthen becomes an exhaust inert gas 219, which may then exhausted from theprocessing chamber. Various embodiments provide that an inert gas 218may flow through the wafer gap region 215 so as to ventilateauto-dopants 217 from the wafer gap region 215, wherein auto-dopants 217comprise dopants that diffuse out of the backside of the substrate 202during a high temperature process. In an embodiment, the hightemperature process comprises an epitaxial deposition.

Embodiments illustrated in FIG. 2C provide for injected reactant gases221 to flow over the front side of the substrate 202, and exhaustreacted gases 222 to flow away from the substrate 202. In embodiments,the substrate 202 may be supported at the edges, which may provide abarrier to the flow of reactant gases 221 onto the backside of thesubstrate 202, thus helping to reduce the deposition of epitaxialmaterial onto the backside of the substrate 202.

FIGS. 9A to 9F illustrate embodiments of the wafer holder structure 203consisting of: a shelf, a bevel, a lip, a protrusion, a finger, or anycombination thereof. FIG. 9A illustrates embodiments wherein the waferholder structure 203 comprises a wafer holder bevel 901, which may beattached to the wafer support ring 220. FIG. 9B illustrates embodimentswherein the wafer holder bevel 901 comprises a notch 902, which seatsthe edge of the substrate 202. FIG. 9C illustrates embodiments whereinthe wafer holder structure 203 comprises a wafer holder shelf 908, whichmay be attached to the wafer support ring 220. FIG. 9D illustratesembodiments wherein the wafer holder structure 203 comprises a waferholder protrusion 909, which may be attached to the wafer support ring220. In embodiments, an alignment ring 910 may be attached to the wafersupport ring 220 and positioned so as to align the substrate 202 ontothe wafer holder protrusion 909. The alignment ring 910 may also act asa barrier to auto-dopants 217 flowing around the edge of the substrate202 from the backside to the front side.

FIGS. 9E and 9F illustrate embodiments wherein the wafer holderstructure 203 comprises a wafer holder finger 912, which may be attachedto the wafer support ring 220. Wafer holder finger 912 may contact thesubstrate 202 in three or more locations. In an embodiment, the thermalmass of the wafer holder finger 912 and the thermal mass of the contactpoint on the substrate 202 match, so as not to cause a cold or hot spoton the substrate 202.

In embodiments, an alignment pin 911 may be located at the inside edgeof the wafer support ring 220, so that substrates 202 being loaded arefurther guided into position. An alignment pin 911 may be used when thesubstrate 202 is located at or below the top plane of the wafer supportring 220, so that the inside wall of the wafer support ring 220 may havethe advantage of serving as a barrier to the flow of auto-dopants 217 tothe front side of the substrate 202. In embodiments, an alignment ring910 may be used when the substrate 202 is positioned above the top ofthe wafer support ring 220, which may provide the advantage of helpingto form a barrier against the flow of gases and materials around theedge of the substrate 202.

Embodiments of the wafer holder structure 203 may comprise the featurethat the wafer holder structure 203 and the substrate 202 form a barrieragainst the passage of gases and materials between the backside of thesubstrate 202 and the front side of the substrate 202, along the entireperimeter of the substrate 202. In some embodiments illustrated in FIGS.2C, and 9A to 9D, the wafer holder structure 203 supports the substrate202 at the edges of the substrate 202. Supporting the substrate 202 atthe edges may provide the advantage of helping to provide a barrier toauto-dopants 217 flowing onto the front side of the substrate 202.

An advantage of isolating the flow of inert gas to the backside of thesubstrate 202 and away from the front side, may result in reducing therisk of auto-doping. In embodiments, the out-diffusion of dopants fromthe backside of the substrate 202 mixes with the inert gas, which isthen exhausted from the processing chamber. In embodiments, the inertgas comprises auto-dopants 217 that may be isolated from the front sideof the substrate 202, where the low doped epitaxial layer is beingformed. This may substantially reduce the risk of contaminating the lowdoped epitaxial layer with auto-dopants 217, which may result insubstantial increases in the resistivity of the epitaxial layers beingformed, while still maintaining good resistivity and thicknessuniformity across the substrate 202.

In embodiments, the inert gas comprises a gas selected from the groupconsisting of: hydrogen, nitrogen, helium, neon, argon, krypton, xenon,radon, or any combination thereof. The inert gas may have the propertyof not chemically interacting with the reactant gases, or the substrate,or the components of the processing apparatus.

FIG. 2A illustrates embodiments in which a spacer 212 may be in contactwith the wafer support ring 220 and positioned on a susceptor plate 205,wherein the spacer 212 positions the wafer support ring 220 above thesusceptor plate 205 to provide a wafer gap region 215 between thesusceptor plate 205 and the backside of the substrate 202.

Embodiments illustrated in FIGS. 9B to 9F comprise interlocking spacerdisks 903. In an embodiment, the interlocking spacer disks 903 furthercomprise a spacer disk protrusion 907, which may fit into either thespacer disk recess 904 of another interlocking spacer disk 903, or thesusceptor positioning hole 906. As illustrated in embodiments in FIG.9F, the area occupied by spacer disk 903 under the wafer support ring220 is only a small fraction of the area of the wafer support ring 220,thus providing ample ventilation of the wafer gap region 215 by the flowof injected inert gas 218, see FIG. 2C. In embodiments, the interlockingspacer disks 903 can be stacked, and thereby may be used to adjust thethickness of the wafer gap region 215.

FIG. 10A and 10B illustrate embodiments comprising the feature of spacerrings 1001. Embodiments may comprise one or more spacer rings 1001,which may be stackable, and may comprise vents 1006, which may permitthe flow of an injected inert gas 218 through the vents 1006 into and/orout of the wafer gap region 215, so as to ventilate the wafer gap region215, thus removing auto-dopants 217. In embodiments, the stackablespacer rings 1001 may interlock with each other. In embodiments, thestackable spacer rings 1001 may interlock with the susceptor plate 205,in which the susceptor plate 205 may comprise a susceptor protrusionring 1004. In embodiments, the stackable spacer rings 1001 may interlockwith the wafer support ring 220, in which the wafer support ring 220 maycomprise a wafer support ring recess 1005.

Embodiment, partially illustrated in FIG. 10B, may comprise radial vents1006, which are directed toward the center of the substrate 202. Inembodiments, the substrate 202 may be rotated, and the spacer ring vents1006, 1007 may comprise a symmetrical pattern, which may improveuniformity. Other embodiments, illustrated in FIG. 10B, may comprisenon-radial vents 1007, which are directed toward regions other than thecenter of the substrate 202. Embodiment may comprise any combination ofradial and non-radial vents 1006 and 1007, which may be suitable foreither or both rotated and stationary substrates 202. In an embodimentillustrated in FIG. 10B, the non-radial vents 1007 may be directed sothat the injected inert gas 218 may flow substantially parallel acrossthe wafer gap region 215, when the substrate 202 is not being rotatedand in a particular orientation. In embodiments, the non-radial vents1007 may be directed so that the injected inert gas 218 may flowsubstantially parallel across the wafer gap region 215 when thesubstrate 202 is oriented in more than two rotational positions. Suchembodiments may provide a pass-through flow more than twice in a singlerotation of the substrate 202. Embodiments may comprise that the exhaustinert gases 219 may flow substantially parallel away from the wafer gapregion 215.

Embodiments may comprise any combination of radial and non-radial vents1006,1007, which may be used to generate turbulent flow patterns ofinjected inert gas 218, which may comprise the formation of one or morevortexes in the wafer gap region 215. Embodiments may further compriserotating the wafer gap region 215, while generating turbulent flowpatterns. Advantages of turbulent flow patterns of injected inert gas218 in the wafer gap region 215 may be to facilitate the mixing andremoval of auto-dopants 217, particularly on and near the surfaces ofstructures internal to the wafer gap region 215, such as the backside ofthe substrate 202. Turbulent flow patterns may have the advantage ofdisrupting the boundary layer on the surfaces of objects in contact withthe flow path of the inert gas 218, and thus increases the removal ofauto-dopants 217 either on or emanating from those surfaces. Anadvantage of increasing the removal of auto-dopants 217 from the wafergap region 215 may be to lower the average concentration of auto-dopants217 in the wafer gap region 215. A lower concentration of auto-dopants217 in the wafer gap region 215 may reduce the amount of auto-dopants217 that may potentially reach the front side of the substrate 202, thusreducing the risk of auto-doping the epitaxial layer formed on the frontside of the substrate 202.

FIGS. 3A and 3B illustrate embodiments of an apparatus for supporting asubstrate 202 above a susceptor plate 205 further comprising a supportring skirt 301 attached to the wafer support ring 220, and which extendsdown toward the susceptor plate 205, wherein the flow of an inert gas218, 219 into and/or out of the wafer gap region 215 is partiallyrestricted, and thus, controlled by the skirt 301. In embodiments, theskirt 301 may comprise a ring having a vertical wall along thecircumference of the wafer support ring 220. In embodiments, the size ofthe skirt gap 315 may be adjusted by the length of the skirt 301 and/orby the adjustable spacer 212. In embodiments wherein the substrate 202is rotated, a longer skirt 301 may provide for a greater auto-dopingpathway 519, but may also reduce the amount of injected inert gas 218that may enter into the wafer gap region 215. The size of the skirt gap315 may be used to adjust the flow of inert gas 218, 219, and degree ofventilation, through the wafer gap region 215, see FIG. 6.

Embodiments illustrated in FIG. 10D wherein the size of the skirt gap315 may be asymmetrical and the substrate 202 may not be rotated. Inembodiments, the skirt gap 315 or intake skirt clearance 1008, on theupwind or injection side of the inert gas flow 218 may be large, whilethe skirt gap 315 or exhaust skirt clearance 1009, on the downwind orexhaust side of the inert gas flow 219 may be small. Such anasymmetrical skirt gap 315 may permit ample flow of inert gas 218 intothe wafer gap region 215, while limiting the exhaust inert gas 219,which contains auto-dopants 217, to exhaust close to the susceptor plate205 and far from the front side of the substrate 202, thus reducing therisk of auto-dopants migrating to the front side of the substrate 202.In an embodiment, a susceptor plate 205 having vents 520 may provide asubstantive means of exhausting inert gas 219 from the wafer gap region215.

FIGS. 5A and 5B illustrate embodiments comprising a skirt 301, which mayfurther comprise skirt vents 518, which may permit the flow of inert gas218, 219 through the skirt vents 518 into and/or out of the wafer gapregion 215. In an embodiment illustrated in FIG. 10C, the distributionof skirt vents 518 may be asymmetrical. In an embodiment, in which thesubstrate 202 may not be rotated, the number and size of skirt vents 518may be high at the injection side of the injection inert gas flow 218and low at the exhaust side of the exhaust inert gas flow 219, so as todirect the inert exhaust gases 219 through the susceptor vents 520 andexhausted from below the susceptor plate 205 far from the front side ofthe substrate 202.

Various embodiments are anticipated for rotated and/or stationarysubstrates 202 during processing, which combine various different sizesof skirt gap 315, both symmetrical and asymmetrical, with variousdifferent sizes and numbers of skirt vents 518, both symmetrically andasymmetrically distributed, which may result in effective ventilation ofauto-dopants 217 from the wafer gap region 215 and remove the inertexhaust gases 219 distal to the front side of the substrate 202.

In embodiments illustrated in FIGS. 5A and 5B, the susceptor plate 205comprises susceptor vents 520. In various embodiments, injected inertgas 218 may flow into the wafer gap region 215 mixing with theauto-dopants diffusing out from the backside of the substrate 202. Theresultant exhaust inert gas 219 may be removed from the wafer gap region215 by either susceptor vents 520, skirt vents 518, skirt gap 315, orany combination thereof, see also FIG. 6. In embodiments, the injectedinert gas 218 may also flow below the susceptor plate 205, mix with theexhaust inert gases 219 flowing out of the wafer gap region 215 throughthe susceptor vents 520, and exhaust out from below the susceptor plate205. An advantage to providing injected inert gas 218 below thesusceptor plate 205 and removing the exhaust inert gases also below thesusceptor plate 205 may be that the flow of auto-dopants 217 may be moredistant from the front side of the substrate 202, which may furtherreduce the risk of auto-doping the deposited epitaxial layer. In someembodiment, the combination of symmetrical and asymmetricallydistributed skirt vents 518 and/or symmetrical and asymmetrical skirtlengths 301 with susceptor vents 520 may be configured to substantiallyrestrict the flow of exhaust inert gases 219 from exhausting above thesusceptor plate 205. This may result in most or almost all of theexhaust inert gas 219 exhausting below the susceptor plate 205, so thatthe susceptor plate 215 may act as a barrier to auto-dopants 217 fromthe front side of the substrate 202.

In embodiments, the susceptor vents 520 may range from about ⅛ to about¼ of an inch. In embodiments, the susceptor plate 205 may comprise amaterial selected from a group consisting of: silicon carbide, graphite,aluminum nitride, other ceramics, or any combination thereof. Inembodiments, the susceptor plate 205 may comprises a porous materialstructure. In embodiments, the susceptor plate 205 may comprises aventilated structure, and thus provide ample flow out from the wafer gapregion 215, through the susceptor plate 205, and under the susceptorplate 205. A porous or ventilated susceptor plate 205 may provide a lowthermal mass, which may result in faster heating and cooling of thesusceptor plate 205, and thus, may facilitate faster heating and coolingof the substrate 202, which may result in higher wafer throughput.

FIGS. 6 and 7 illustrate embodiments that may comprise a support ringskirt 301 attached to the wafer support ring 220 and extends down towardthe susceptor plate 205, wherein the flow of inert gas 218, 219 intoand/or out of the wafer gap region 215 may be partially restricted, andthus, controlled by the skirt 301. Further embodiments of the waferprocessing structure 200 illustrated in FIGS. 6 and 7 may furthercomprise a shelf extension 204, 704 positioned between and attached tothe wafer support ring 220 and the wafer holder structure 203. FIG. 6illustrates embodiments, which may comprise a small shelf extension 204,whereas the embodiments illustrated in FIG. 7, may comprises a largeshelf extension 704.

Embodiments illustrated in FIG. 5B may comprise a small shelf extension204, which may position the front side of the substrate 202 proximate tothe plane of the top of the wafer support ring 220. Auto-dopants 217 maymigrate approximately along an unextended auto-doping pathway 519.Embodiments illustrated in FIG. 7 may comprise a large shelf extension704, which may position the front side of the substrate 202substantially distant from the plane of the top of the wafer supportring 220. The substrate 202 may be positioned in a valley surrounded bythe wafer processing structure 200, which overlooks the substrate 202.Auto-dopants 217 may migrate approximately along an extended auto-dopingpathway 719, which is longer and more likely to result in a greaterreduction of auto-doping of the epitaxial layer on the front side of thesubstrate 202.

FIG. 10E illustrate embodiments wherein the support ring skirt 301further comprises skirt vents 518, which may further comprise turbineskirt blades 1010, wherein the turbine skirt blades 1010 during rotationof the wafer support ring 220 and support ring skirt 301, facilitate theintake and/or exhaust of inert gases 218, 219 into and/or out of thewafer gap region 215. In embodiments, the turbine skirt blades 1010 maybe attached to the support ring skirt 301 proximate to the trailing sideof the skirt vents 518, wherein the trailing side of the skirt vent 518may be described as the last side to reach a fixed point when the skirtis being rotated in a particular rotation direction 1011. Inembodiments, the turbine skirt blades 1010 may be formed from thesupport ring skirt 301 while also forming the turbine skirt vents 1012.In embodiments, the turbine skirt vent 1012 may be formed by cutting theskirt 301 on three of the four sides of the vent 1012. In embodiments,the skirt material may still be attached to the edge of the vent 1012and may be bent outward, so as to protrude from the outside of the wafersupport ring 220 and skirt 301. The protruding skirt material, stillattached to the skirt 301 may be used as the turbine skirt blades 1010.

In embodiments, wherein the turbine skirt blade 1010 may be directed outfrom the point of attachment to the skirt 301 in the direction ofrotation 1011, then the turbine blades 1010 may increase the pressure ofinert gas in the wafer gap region 215 proportional to the rotationalspeed of the turbine blades 1010. In embodiments wherein the turbineblades 1010 may be directed opposite the direction of rotation 1011,then the turbine blades 1010 may decrease the pressure of inert gas inthe wafer gap region 215 proportional to the rotational speed of theturbine blades 1010. Some embodiments may include various combinationsof skirt vents 518 and turbine blades 1010, which may be directed ineither the same or opposite the direction of rotation 1011. Embodimentmay comprise two rings of structures in the support ring skirt 301,wherein the top ring of structures may comprise skirt vents 301 and/orturbine skirt vents 1012 having turbine blades 1010 co-directional withthe direction of rotation 1011, and wherein the bottom ring ofstructures may comprise turbine skirt vents 1012 having turbine blades1010 opposite the direction of rotation 1011. Such a configuration mayfacilitate the intake of inert gas 218 at the top ring of structures andexhaust inert gas 219 at the bottom ring of structures, whereby a flowpattern may be generated that provides a flow of inert gas 218 near thebackside of the substrate 202 and exhausts the mixture of inert gas 219and auto-dopants 217 out near the susceptor plate 205, thus increasingthe auto-doping pathway 519.

FIGS. 11 and 13 illustrate embodiments of an apparatus 1100, 1300 fordepositing an epitaxial layer on a substrate 202, which may comprise aprocessing chamber 113; a susceptor plate 205 within the processingchamber 113; a wafer processing structure 200 for supporting a substrate202 over the susceptor plate 205; wherein the substrate 202 comprises afront side and a backside; wherein the front side faces up and thebackside of the substrate 202 faces down towards the susceptor plate205; wherein the wafer processing structure 200 may comprise a wafersupport ring 220 and a wafer holder structure 203 attached to the wafersupport ring 220. In embodiments, the apparatus 1100, 1300 may furthercomprise a spacer 212 in contact with the wafer support ring 220 andpositioned on the susceptor plate 205, wherein the spacer 212 positionsthe wafer support ring 220 above the susceptor plate 205 to provide awafer gap region 215 between the susceptor plate 205 and the backside ofthe substrate 202.

In embodiments, the apparatus 1100,1300 may further comprise an upperinjection manifold 1106 for providing reactant gases 221 into theprocessing chamber 100 and onto the front side of the substrate 202; alower injection manifold 1107 for providing an inert gas 218 into theprocessing chamber 113 proximate to the wafer gap region 215; and alower exhaust manifold 1109 for removing exhaust gases 1108 containingauto-dopants 217 from the processing chamber 113. In embodiments, theexhaust gases 1108 may comprise inert gas 219 containing auto-dopants217 from the backside of the substrate 202. Embodiments may furthercomprising a reacted gases exhaust port 1115 for removing reacted andresidual reactant gases 222 from the region over the front side of thesubstrate 202, whereby reactant gases may be distanced from the backsideof the substrate 202. In embodiments, the reacted gases exhaust port1115 further comprises a flow control valve 1110, which may be used tocontrol the flow of exhaust reacted gases 222.

Embodiments may further comprise upper and lower injection manifolds1106, 1107 and upper and lower exhaust ports 1115, 1116, 1117 to providea means for separating and isolating the flow of reactant gases 222 onthe front side of the substrate 202 away from the flow of inert gas 218on the backside of the substrate 202. Separating and isolating reactantgases 222 from the backside of the substrate 202 may reduce the risk ofdepositing epitaxial material on the backside of the substrate 202.Epitaxial deposits on the backside of the substrate 202 may likelyrequire that the deposits be removed later, which may increase the riskof backside defects, such as scratches and haze.

Embodiments illustrated in FIG. 11 may comprise one or more reactantinjection ports 1111, 1112 in communication with the upper injectionmanifold 1106. Embodiments may comprise an edge reactant gases injectionport 1112 providing reactant gases 221, which may flow across thesubstrate 202, which in embodiments may be rotated during processing.Embodiments may further comprise a flow control valve 1110 to controlthe flow of reactant gases 221 from the edge reactant gases injectionport 1112. Embodiments may further comprise a center reactant gasesinjection port 1111, which may be located proximate to the center of thesubstrate 202. Embodiments may further comprise a flow control valve1110 to control the flow of reactant gases 221 from the center reactantgases injection port 1111. A center reactant gases injection port 1111,located proximate to the center of a rotating substrate 202, may provideimproved thickness uniformity since the edge injection port 1112 wouldlikely provide fresh reactants to the edges of the substrate 202.However, without a direct flow of reactants to the center, the centermay likely be provided with only partially used reactants. Therefore,the center port 1111 may provide fresh reactants to the center, whichmay increase the growth of epitaxial material in the center of thesubstrate 202, which may facilitate thickness uniformity of theepitaxial layer being formed on the front side of the substrate 202. Inembodiments, the upper injection manifold 1106 may further comprise aplurality of outlets and/or ports over the front side of the substrate202. In embodiments, the upper injection manifold 1106 may furthercomprise a showerhead of inlets and/or outlets over the front side ofthe substrate 202.

Embodiments illustrated in FIG. 11 may comprise one or more inert gasinjection ports 1113, 1114 in communication with the lower injectionmanifold 1107. Embodiments may comprise an upper inert gas injectionport 1113, located above the susceptor plate 205, providing inert gas218, which may flow into the wafer gap region 215, which in embodimentsmay be rotated. Embodiments may further comprise a flow control valve1110 to control the flow of inert gas 218 from the upper inert gasinjection port 1113. Embodiments may further comprise a lower inert gasinjection port 1114, which may be located below the susceptor plate 205.Embodiments may further comprise a flow control valve 1110 to controlthe flow of inert gas 218 from the lower inert gas injection port 1114.In embodiments, the susceptor plate 205 may comprising susceptor vents520, which may provide additional ventilation of the wafer gap region215. In embodiments, the susceptor vents 520 may range from about ⅛ toabout ¼ of an inch.

FIG. 11 illustrates embodiments that may comprise one or more exhaustports 1115, 1116, 1117 in communication with an exhaust manifold 1109,which may be used to facilitate the control of flow patterns of inertgas 218 and reactant gases 221. Embodiments may further comprise thatany or all of the exhaust ports may be further controlled with flowcontrol valves 1110. In some embodiments, the exhaust flow of inertgases 219 in the lower inert gases exhaust port 1117 may be adjusted toa high flow rate, to provide a net downward flow. A net downward flowmay provide better drawdown of auto-dopants 217 from the wafer gapregion 215 through the susceptor vents 520, thus providing furtherdistancing of the auto-dopants 217 from the front side of the substrate202. A net downward flow may also provide a net downward force on thesubstrate 202, helping to keep the substrate 202 on the wafer processingstructure 200.

Embodiments illustrated in FIGS. 13, 11, 8, and 1A may comprisesusceptor arms 1105, which may be attached to a shaft that may permitthe susceptor plate 205 and wafer processing structure 200 to move upand down. In embodiments, the up position may be used during theepitaxial deposition, while the down position may be used to permit fortransferring the substrate 202. In embodiments, not shown in FIG. 11 forthe purpose reducing clutter in the drawing, but illustrated in FIGS.13, 8 and 1A, may comprise lift fingers 801, which may have liftcontacts 803, and which move through lift through holes 802 in thesusceptor plate 205, and which are attached to lift arms 101. Inembodiments, the lift fingers 801 may separate the substrate 202 fromthe wafer processing structure 200, so that the substrate 202 may beremoved by a robot (not shown) from the chamber 113, and then loadedwith another substrate 200 for processing. Epitaxial depositions in theupper section of the processing chamber 113 may have the advantage ofbetter control of process gas flows and temperatures than in the lowersection of the processing chamber 113.

Embodiments illustrated in FIGS. 11 and 13 may comprise that thesubstrate 202 on the positioned wafer support ring 220 may beapproximately parallel to the susceptor plate 205. In embodiments, thetopside of the susceptor plate 205, which faces the backside of thesubstrate 202, may be approximately flat. Embodiments may comprise thatthe spacers 212 are adjustable thereby providing a means for adjustingthe thickness of the wafer gap region 215. Embodiments may comprise thatthe spacers 212 may be detachable from the wafer support ring 220 andmay be replaced with different sized spacers 212. In embodiments, thespacer 212 may comprise a protrusion 417, which fits into a slot 213 inthe susceptor plate 205. In some embodiments, the susceptor plate 205may comprise a structure for interlocking with the spacer 212 selectedfrom the group consisting of: a recess, a protrusion, a locking pin, ora combination thereof. In embodiments, the wafer support ring 220 andthe spacer 212 may be detachable from the susceptor plate 205. Inembodiments, the wafer holder structure 200 may be selected from thegroup consisting of: a shelf, a bevel, a lip, a protrusion, a finger, orany combination thereof.

Embodiments may comprise a skirt 301 wherein the skirt may comprisevents 518, which permit the flow of an inert gas 218, 219 through thevents 518 into and/or out of the wafer gap region 215. In embodiments,the wafer gap region 215 may have a thickness of about 0.1 inches toabout 0.3 inches. Embodiments provide a means for ventilatingauto-dopants 217 from the wafer gap region 215 with inert gas 218,wherein the auto-dopants 217 comprise dopants that diffuse out of thebackside of the substrate 202 during the epitaxial deposition.

Embodiments may provide the means for ventilating the wafer gap region215 that may comprise flowing substantial amounts of inert gas 218through the wafer gap region 215. Flowing substantial amounts of inertgas 218 through the wafer gap region 215 may provide that mixing ofinert gas 218 with auto-dopants 217 is the predominant mechanism bywhich auto-dopants 217 may be removed from the wafer gap region 215.Mixing may be a much more effective means for extracting auto-dopants217, than by a predominantly diffusive mechanism. Embodiments mayprovide that the inert gas 218 comprises a gas selected from the groupconsisting of: hydrogen, nitrogen, helium, neon, argon, krypton, xenon,radon, or any combination thereof.

Embodiments illustrated in FIGS. 11, 12, and 13 may provide a method ofusing an epitaxial apparatus 1100, 1300 that supports a substrate 202above a susceptor plate 205 for depositing an epitaxial layer on thesubstrate 202, which may comprise providing a spacer 212 and a waferprocessing structure 200 onto a susceptor plate 205 in a processingchamber 113 of an epitaxial reactor apparatus 1100, 1201, 1300; whereinthe wafer processing structure 200 may comprise a wafer support ring 220and a wafer holder structure 203 attached to the wafer support ring 220;providing a substrate 202, 1202; wherein the substrate 202 comprises afront side and a backside; wherein the spacer 212 may be in contact withthe wafer support ring 220 and positioned on the susceptor plate 205,wherein the spacer 212 may position the wafer support ring 220 above thesusceptor plate 205 to provide a wafer gap region 215 between thesusceptor plate 205 and the backside of the substrate 202; wherein thebackside of the substrate 202 may comprises a heavily dopedsemiconductor; flowing an inert gas 218 into the processing chamber 113proximate to the wafer gap region 215 and below the backside of thesubstrate 202, 1203; flowing reactant gases 221 into the processingchamber 113 onto the front side of the substrate 202, 1204; growing alightly doped epitaxial semiconductor layer on the front side of thesubstrate 202 from the reactant gases 221, 1205; and exhausting theinert gas 219 containing auto-dopants 217 out from the wafer gap region215 and below the top of the wafer processing structure 200 out of theprocessing chamber 113, 1206.

In embodiments, the reactant gases 221 may comprise a silicon precursorgas used to form a single crystal silicon or single crystalsilicon-germanium epitaxial layer. Embodiments of a silicon precursorgas may comprise SiH₄ or silane gas. In embodiments, the reactant gases221 may further comprise a germanium precursor used to form a singlecrystal silicon-germanium epitaxial layer. Embodiments of a germaniumprecursor gas may comprise GeH₄. In embodiments, the reactant gases 221may further comprise one or more dopant precursors used to dope thesingle crystal epitaxial layer. Embodiments of a dopant precursor gasmay comprise diborane or borane.

In embodiments, growing the lightly doped epitaxial semiconductor layermay comprise growing a lightly doped single crystal silicon layer or alightly doped single crystal silicon-germanium layer. In embodiments,the dopant may comprise boron. In embodiments the growth of the singlecrystal silicon epitaxial layer may occur at a temperature greater thanabout 950° C. In embodiments, the growing of the single crystal siliconepitaxial layer on the front side of the substrate 202 may occur at atemperature greater than about 1050° C. In embodiments, the growing ofthe silicon-germanium epitaxial layer on the front side of the substrate202 may occur at a temperature greater than about 850° C. Inembodiments, the growing of the silicon-germanium epitaxial layer mayoccur at a temperature greater than about 950° C.

Embodiments may further comprise ventilating the wafer gap region 215with a flow of inert gas 218 while growing the lightly doped epitaxialsemiconductor layer on the front side of the substrate 202, therebyremoving auto-dopants 217 diffusing out from the backside of thesubstrate 202, which may substantially reduce the amount of auto-dopants217 that reach the front side of the substrate 202. Embodiments maycomprise reducing the concentration of auto-dopants 217 incorporatedinto the lightly doped epitaxial semiconductor layer on the front sideof the substrate 202.

Embodiments may further comprise rotating the susceptor plate 205, thewafer processing structure 200, and the substrate 202. Embodiments maycomprise rotating the susceptor plate 205, the wafer processingstructure 200, and the substrate 202, at a rotational speed of about 3rpm to about 300 rpm. An embodiment may comprise rotating the substrate202 at a rotational speed of about 20 rpm to about 60 rpm.

In embodiments, the ventilating of the wafer gap region 215 may furthercomprise adjusting the flow of inert gas 218 to improve ventilation andreduce the risk of contaminating the epitaxial layer with auto-dopants217 and reduce the risk of depositing epitaxial material on the backsideof the substrate 202. In embodiments, adjusting the flow of inert gas218 further comprises adjusting the thickness of the wafer gap region215 by adjusting the height of the spacers 212. In embodiments, thethickness of the wafer gap region 215 may be selected to be thick enoughto substantially reduce auto-doping but not too thick to substantiallydegrade temperature uniformity, thereby degrading the thicknessuniformity of the deposited epitaxial layer formed on the front side ofthe substrate 202. Substantial reductions in auto-doping and substantialimprovements in thickness uniformity, may result in higher resistivitiesand improved quality of the epitaxial layer, which may provide improvedperformance and potential for new applications for devices, for example,semiconductor devices, manufactured on such epitaxial layers. Inembodiments, the wafer gap region 215 may have a thickness of about 0.1inches to about 0.3 inches. Embodiments for adjusting the flow of inertgas 218 may further comprises the methods selected from the groupconsisting of: adjusting gap size, adjusting skirt length, adjusting thenumber, size, and positions of vents, adjusting the speed of rotation ofthe wafer processing structure 200, adjusting the positions of injectionand exhaust ports, adjusting the flow rates of injected inert gas 218,adjusting the flow rates of exhaust inert gas 219, adjusting the flowrates of injected reactant gases 221, adjusting the flow rates ofexhaust reacted gases 222, and any combination thereof.

In embodiments, the inert gas may comprise a gas selected from the groupconsisting of: hydrogen, nitrogen, helium, neon, argon, krypton, xenon,radon, or any combination thereof. The inert gas may comprise any gasthat would not interact with or interfere with the reactions occurringin the processing chamber. In embodiments, the wafer processingstructure 200 and the spacers 212 may provide a means for separating andisolating reactant gas 221 flow patterns on the front side of thesubstrate from inert gas 218 flow patterns on the backside of thesubstrate 202. In embodiments, the flow of inert gas 218 may furthercomprise a pre-curser flow prior to the epitaxial deposition and aprocessing flow during the epitaxial deposition. In embodiments, thepre-curser flow may be about 2 l/min to about 40 l/min. Sufficientpre-curser flow may be effective in removing residual auto-dopants 217from the previously processed substrate 202. In embodiments, theprocessing flow may be about 20 l/min to about 180 l/min. Sufficientprocessing flow may be effective in maintaining a low concentration ofauto-dopants 217 in the wafer gap region 215.

In embodiments, the flowing of reactant gases 221 onto the front side ofthe substrate 202 may further comprise flowing reactant gases 221through multiple or adjustable injection ports. The use of multiple oradjustable injection ports may be effective in improving bothresistivity and thickness uniformity. In embodiments, the flowing ofreactant gases 221 onto the front side of the substrate 202 throughmultiple or adjustable injection ports may further comprise providingextra dopant in the center of the substrate 202.

In embodiments, the heavily doped semiconductor on the backside of thesubstrate 202 may comprise boron. In embodiments, the heavily dopedsemiconductor on the backside of the substrate 202 may have aresistivity less than about 100 milliohms/sq. In embodiments, thelightly doped epitaxial semiconductor on the front side of the substrate202 may have a resistivity between about 5 ohms/sq. to about 150ohms/sq. In embodiments, the growing of the epitaxial layer on the frontside of the substrate 202 may occur at a temperature greater than about950° C. In embodiments, the growing of the epitaxial layer on the frontside of the substrate 202 may occur at a temperature greater than about1050° C. Deposition rates may increase with the deposition temperature,but so may diffusion of auto-dopants 217 from the backside of thesubstrate 202. Therefore, providing the means to reduce auto-dopingprovides the ability to increase process temperatures, and thus, mayincrease apparatus 1300 throughput.

Embodiments may further comprise a computer with instructions, which maybe stored on a computer readable medium, to facilitate the control ofembodiments of processes for a method of using various embodiments ofreduced auto-doping epitaxial apparatus 1300. The instructions tocontrol processes may comprise main process control instructions. Inembodiments, the main process control instructions may compriseinstructions to control the flow rates and/or flow patterns of injectedinert gas 218 and/or injected reactant gases 221. In embodiments, themain process control instructions may further comprise instructions tocontrol the flow rates and/or flow patterns of exhaust inert gases 219and/or exhaust reacted gases 222. In embodiments, the main processcontrol instructions may further comprise instructions to control thecomposition of the injected reactant gases 221, which may furthercomprise control of one or more of the flow rates of individualconstituents of the injected reactant gases 221. In embodiments, themain process control instructions may further comprise instructions tocontrol the distribution and concentration of dopants in the reactantgases 221 flowing over the surface of the front side of the substrate202. In embodiments, the main process control instructions may furthercomprise instructions to control the flow rates and/or flow patterns ofone or both of the pre-curser flow and the processing flow of injectedinert gas 218. In embodiments, the main process control instructions mayfurther comprise instructions to control the ventilation of the wafergap region 215.

In embodiments, the main process control instructions may furthercomprise instructions to control the processing temperatures, and/orramp-up temperature profiles, and/or cool-down temperature profiles,and/or temperature uniformity across the substrate. In embodiments, themain process control instructions may further comprise instructions tocontrol the rotational speeds of the substrate being processed.Embodiments may comprise rotational speed profiles before, and/orduring, and/or after the epitaxial growth process.

Embodiments illustrated in FIGS. 11 and 13 may provide for an apparatus1100, 1300 for reducing auto-doping of the front side of a substrate 202and defects on the backside of the substrate 202 during an epitaxialdeposition process. Embodiments may comprise: a means for forming awafer gap region 215 having an adjustable thickness, wherein the wafergap region 215 may comprise a region between the backside of thesubstrate 202 and a susceptor plate 205; a means for ventilatingauto-dopants 217 out of the wafer gap region 215 with a flow of inertgas 218, while inhibiting or prohibiting the flow of inert gas 218 overthe front side of the substrate 202; and a means for flowing reactantgases 221 over the surface of the front side of the substrate 202, whileinhibiting or prohibiting the flow of reactant gases 221 near thesurface of the backside of the substrate 202.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative and not restrictive of the current invention, andthat this invention is not restricted to the specific constructions andarrangements shown and described since modifications may occur to thoseordinarily skilled in the art.

What is claimed:
 1. An apparatus for supporting a substrate above asusceptor plate comprising: a wafer processing structure for supportinga substrate; wherein the substrate comprises a front side and abackside; wherein the wafer processing structure comprises: a wafersupport ring; and a wafer holder structure attached to the wafer supportring, wherein the wafer holder structure supports the substrate in aposition for processing; and a spacer in contact with the wafer supportring and positioned on top of a susceptor plate, wherein the spacerpositions the wafer support ring above the susceptor plate to provide awafer gap region between the susceptor plate and the backside of thesubstrate and wherein the spacer is adjustable to adjust the thicknessof the wafer gap region.
 2. The apparatus of claim 1, wherein an inertgas is capable of flowing through the wafer gap region so as toventilate auto-dopants from the wafer gap region, wherein auto-dopantscomprise dopants that diffuse out of the backside of the substrateduring a high temperature process.
 3. The apparatus of claim 2, whereinthe high temperature process comprises an epitaxial deposition.
 4. Theapparatus of claim 2, wherein the inert gas comprises a gas selectedfrom the group consisting of: hydrogen, nitrogen, helium, neon, argon,krypton, xenon, radon, or any combination thereof.
 5. The apparatus ofclaim 1, wherein the wafer holder structure is selected from the groupconsisting of: a shelf, a bevel, a lip, a protrusion, a finger, or anycombination thereof.
 6. The apparatus of claim 1, wherein the waferholder structure supports the substrate at the edges of the substrate.7. The apparatus of claim 1, wherein the positioned wafer support ringsupports a substrate that is approximately parallel to the susceptorplate.
 8. The apparatus of claim 1, wherein the wafer support ring,wafer holder structure, and spacer comprise one or more materialsselected from a group consisting of: silicon carbide, quartz, graphite,silicon nitride, aluminum nitride, or any combination thereof.
 9. Theapparatus of claim 1, wherein the thickness of the walls of the wafersupport ring are between about 0.002 inches to about 0.3 inches.
 10. Theapparatus of claim 1, wherein the spacer is detachable from the wafersupport ring and replaceable with a different sized spacer.
 11. Theapparatus of claim 10, wherein the spacer comprises a stand-off pin. 12.The apparatus of claim 11, wherein the stand-off pin comprises aprotrusion, which fits into a slot in the susceptor plate.
 13. Theapparatus of claim 1, wherein the spacer comprises one or more spacerrings, which are stackable, and comprise vents, which permit the flow ofan inert gas through the vents into and/or out of the wafer gap region.14. The apparatus of claim 13, wherein the one or more stackable spacerrings interlock with each other and with the susceptor plate and thewafer support ring.
 15. The apparatus of claim 1, further comprising askirt attached to the wafer support ring and extends down toward thesusceptor plate, wherein the flow of an inert gas into and/or out of thewafer gap region is controlled by the skirt.
 16. The apparatus of claim15, wherein the skirt comprises a ring having a vertical wall along thecircumference of the wafer support ring.
 17. The apparatus of claim 16,wherein the skirt comprises vents, which permit the flow of an inert gasthrough the vents into and/or out of the wafer gap region.
 18. Theapparatus of claim 1, wherein the topside of the susceptor plate, whichfaces the backside of the substrate, is approximately flat.
 19. Theapparatus of claim 1, wherein the wafer gap region has a thickness ofabout 0.1 inches to about 0.3 inches.
 20. The apparatus of claim 1,wherein the wafer processing structure is slightly inclined with respectto the susceptor plate, wherein the substrate held by the waferprocessing structure is slightly lower on an injection side and slightlyhigher on an exhaust side.
 21. The apparatus of claim 1, wherein thewafer support ring and the spacer are detachable from the susceptorplate.
 22. An apparatus for depositing an epitaxial layer on a substratecomprising: a processing chamber; a susceptor plate within theprocessing chamber; a wafer processing structure for supporting asubstrate over the susceptor plate; wherein the substrate comprises afront side and a backside; wherein the wafer processing structurecomprises: a wafer support ring; and a wafer holder structure attachedto the wafer support ring; a spacer in contact with the wafer supportring and positioned on top of the susceptor plate, wherein the spacerpositions the wafer support ring above the susceptor plate to provide awafer gap region between the susceptor plate and the backside of thesubstrate and wherein the spacer is adjustable to adjust the thicknessof the wafer gap region; an upper injection manifold for providingreactant gases onto the front side of the substrate; a lower injectionmanifold for providing an inert gas into the processing chamberproximate to the wafer gap region; and a lower exhaust manifold forremoving exhaust gases containing auto-dopants from the processingchamber.
 23. The apparatus of claim 22, wherein the inert gas comprisesany gas or combination of gases that would not interact with orinterfere with the reactions occurring in the processing chamber. 24.The apparatus of claim 22, wherein the topside of the susceptor plate,which faces the backside of the substrate, is approximately flat. 25.The apparatus of claim 22, wherein the substrate on the positioned wafersupport ring is approximately parallel to the susceptor plate.
 26. Theapparatus of claim 22, wherein the susceptor plate comprises a materialselected from a group consisting of: silicon carbide, graphite, aluminumnitride, other ceramics, or any combination thereof.
 27. The apparatusof claim 22, wherein the wafer holder structure is selected from thegroup consisting of: a shelf, a bevel, a lip, a protrusion, a finger, orany combination thereof; and wherein the wafer support ring and thespacer are detachable from the susceptor plate.
 28. The apparatus ofclaim 22, further comprises an upper reacted gases exhaust port forremoving reacted gases and residual reactant gases from the region overthe front side of the substrate.
 29. The apparatus of claim 28, whereinthe upper and lower injection manifolds and the upper and lower exhaustports provide a means for separating and isolating reactant gas flowpatterns on the front side of the substrate from inert gas flow patternson the backside of the substrate.
 30. The apparatus of claim 22,providing a means for ventilating auto-dopants from the wafer gap regionwith inert gas, wherein auto-dopants comprise dopants that diffuse outof the backside of the substrate during the epitaxial deposition. 31.The apparatus of claim 30, wherein the means for ventilating comprisesflowing substantial amounts of inert gas through the wafer gap region.32. The apparatus of claim 22, wherein the susceptor plate comprisessusceptor vents.
 33. The apparatus of claim 32, wherein the susceptorvents range from about ⅛ to about ¼ of an inch.
 34. The apparatus ofclaim 22, wherein the susceptor plate comprises a porous materialstructure.
 35. The apparatus of claim 22, wherein the susceptor platecomprises a ventilated structure, wherein the ventilated structureprovides substantial flow out of the wafer gap region.
 36. The apparatusof claim 22, wherein the susceptor plate comprises a structure forinterlocking with the spacer selected from the group consisting of: arecess, a protrusion, a locking pin, or a combination thereof.
 37. Theapparatus of claim 22, further comprising a skirt attached to the wafersupport ring and extends down toward the susceptor plate, wherein theflow of an inert gas into and/or out of the wafer gap region iscontrolled by the skirt.
 38. The apparatus of claim 37, wherein thewafer processing structure further comprises a shelf extensionpositioned between and attached to the wafer support ring and the waferholder structure.
 39. The apparatus of claim 22, wherein the upperinjection manifold further comprises a showerhead of inlets and/oroutlets over the front side of the substrate.
 40. An apparatus forreducing auto-doping of the front side of a substrate and defects on thebackside of the substrate during an epitaxial deposition process fordepositing an epitaxial layer on the front side of the substratecomprising: a means for forming a wafer gap region having an adjustablethickness, wherein the wafer gap region comprises a region between thebackside of the substrate and a susceptor plate; a means for ventilatingauto-dopants out of the wafer gap region with a flow of inert gas, whileinhibiting or prohibiting the flow of inert gas over the front side ofthe substrate; and a means for flowing reactant gases over the surfaceof the front side of the substrate, while inhibiting or prohibiting theflow of reactant gases near the surface of the backside of thesubstrate.